A sensitivity study of near-field thermomechanical conditions in tuff
A study was conducted by the Pacific Northwest Laboratory to investigate the response of a discontinuous rock mass to the combined mechanical and thermal loads from the excavation of repository openings and decay heating of radioactive waste forms. The ANSYS finite element code was used to calculate temperatures and thermal stresses near an emplacement hole as a function of time. The UDEC distinct element code was used to simulate a discontinuous rock mass around the emplacement hole using the finite element stress results as boundary conditions. This approach differs from previous work in its approximation of the near-field geosphere as an assemblage of blocks that are free to slide and rotate relative to one another. The physical properties of the rock joints and fractures were explicitly included in the analysis. Earlier efforts have used continuum models that included the effects of discontinuities by adjusting material properties (reducing elastic modulus and rock strength) or using ubiquitous joints. A range of parameter values were used to represent the upper, lower, and expected conditions for the Yucca Mountain site. Assuming worst case conditions, the calculated displacements around the emplacement hole were only a small fraction of the design air gap between the waste package and the wall of the emplacement hole. Overall, the results confirm that the retrieval option and waste package lifetime will not be adversely affected by borehole instability and excessive rock loads. 8 refs., 6 figs., 4 tabs.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (United States)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 137550
- Report Number(s):
- PNL-SA--16734; CONF-890928--14; ON: DE90002663
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DESIGN
GEOLOGIC FRACTURES
HIGH-LEVEL RADIOACTIVE WASTES
MINE SHAFTS
RADIOACTIVE WASTE FACILITIES
RADIOACTIVE WASTE MANAGEMENT
ROCK MECHANICS
SENSITIVITY ANALYSIS
SITE CHARACTERIZATION
STRESS ANALYSIS
TEMPERATURE DEPENDENCE
TUFF
UNDERGROUND DISPOSAL
YUCCA MOUNTAIN
Yucca Mountain Project